1. Technical Field of the Embodiment
The present embodiment relates in general to a method and apparatus for the continuous curing and post curing of strands of extruded rubber products and the like. More specifically, the present embodiment relates to a method and apparatus that can continuously perform both curing and/or post curing processes of strands of extruded rubber and similar products.
2. Description of the Related Art
Several types of apparatuses and methods are employed for the continuous curing of longitudinally extruded strands of rubber and similar products. Conventional apparatuses offer discontinuous or batch processes for curing rubber and related extruded strands. The conventional apparatus and methods typically cure continuous lengths of extruded strands in a continuous fashion in a liquid salt bath or curing oven with heat and/or through a microwave process, and are then post-cured in a batch fashion where the extrudate is cut and post-cured in an oven or autoclave. The conventional method of batch post-curing is inefficient due to the presence of multiple manufacturing processes, increased labor, and resulting overhead expenses.
Various apparatuses and methods exist for the curing of different types of materials. U.S. Pat. No. 4,155,695 issued to Karppo on May 22, 1979 discloses an apparatus for continuous curing of elongated products, such as cables comprising a conductor surrounded by a mantle of cross linkable material. The cable is passed longitudinally through a curing tube for heating the cable to a curing temperature and subsequently subjected to cooling. The heating of the cable in the heating zone is carried out by means of heat radiation in a pressurized gas atmosphere and the cooling of the cable is carried out in the presence of a gas under pressure so that heat is transferred from the heated cable in the cooling zone partially by radiation to the cooled wall of the tube and partly by convection to said cooled gas.
U.S. Pat. No. 4,356,143 issued to Hill on Oct. 26, 1982 discloses an apparatus and a method for the curing of a continuous length of curable material. The length of material is passed through a curing chamber defined by a tubular body. This tubular body is disposed in the upper part of another heated tubular body which contains a heat exchange liquid. This liquid is fed to one or more injectors disposed at one or both ends of the body, injected along the chamber, and then allowed to drain back into the body. The body contains a further tubular body downstream of, and partitioned from, the original tubular body. The tubular body also has an injector through which water is injected to cool the length of material. The tubular body may be provided with drain holes through which heat exchange liquid can be quickly drained at the end of a curing run. It may also be provided with air vents or a longitudinal slot in its upper part to release trapped air. Devices for wiping heat exchange liquid clinging to the cured material on emergence from the curing chamber are also provided.
U.S. Pat. No. 7,198,476 issued to Harcourt on Apr. 3, 2007 discloses an apparatus and process for continuously vulcanizing a hose. Pressurized air or other gas is intermittently supplied through a woven jacket, a mandrel, a check valve and into the interior of an extruded rubber hose. The hose is sealed as it is pulled over the mandrel. Pinch rollers seal the other end of the hose. One or more non-contact heaters vulcanize the hose from outside-in. Pressurizing the inside of the hose maintains proper diametrical dimensions of the hose.
The above conventional apparatuses and methods employ batch processing of the extrudate in the cooling zone, and uses pressurized hot air or other gas in the heating zone. Generally these conventional apparatuses and methods cure in a continuous fashion in a liquid salt bath or curing oven with heat and/or microwaves; and are then post-cured in a batch fashion where the extrudate is cut and post-cured in an oven or autoclave. These methods cannot be employed for the simultaneous and continuous curing of multiple strands of the extrudate.
Hence, it can be seen that there is a need for an improved method and apparatus for the continuous curing of extrudates. Continuous curing is preferred to the discontinuous curing processes because the quality of the final product is higher due to the ability to accommodate longer extrudates and easier quality control. The continuous curing method is also more economical due to the presence of high speed lines and the absence of the need for the intermediate conveying of the extrudate. Lower overall costs as a result of less manpower, less space requirements, and lower energy requirements are additional benefits realized as a result of using the continuous curing method and apparatus.